An investigation of the structure is complete. Deputy Fire Chief Hunter told WFMY News 2 they sent several items to a forensics lab, but would not reveal what the items were at this time. Therefore, an exact cause won't be known for at least three weeks, he said.

"The fire was unfortunate, but we are grateful that it was accidental," said Hunter.

About 75 firefighters were dispatched to the four-alarm fire at the vacant apartment complex on West Lee Street March 14.